Power saving method and apparatus for intermittently reading reproduction apparatus

ABSTRACT

A reproducing or recording/reproducing apparatus having a constitution in which produced data read from a recording medium is stored in memory at a first transfer rate in a unit time and the stored data is read at a second transfer rate lower than the first transfer rate in the unit time. An operation of means for reading the reproduced data from the recording medium is stopped when an mount of the data accumulated in the storage means gets larger than a predetermined amount, allowing to save the power for driving the apparatus.

This is a divisional of application Ser. No.08/088,674, filed Jul. 7,1993.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an audio reproducing apparatus forreproducing data from, for example, a disc recording medium.

2. Description of the Related Art

It is known in the art that a reproducing-only apparatus orrecording/reproducing apparatus on which a magneto-optical disc or anoptical disc is operated for audio reproduction is required to operateon as small an electric power as possible for a longer playback time.This requirement is especially conspicuous with a portable, compactapparatus with its power supplied from an internally installed batterysuch as a dry battery or a rechargeable battery.

Meanwhile, U.S. Ser. No. 717700 filed Jun. 19, 1991 for examplediscloses a reproducing apparatus for reproducing data from amagneto-optical disc or an optical disc (such as a compact disc) whereinthe data read from a recording medium through an optical head istemporarily stored in a buffer memory unit from which it is read at apredetermined timing to be converted into a reproduced audio signal.

In the above-mentioned constitution, a bit transfer rate at which thedata read through the optical head is sent to the buffer memory is setto a higher level than a rate at which the data is read from the buffermemory. Consequently, the data is written to the buffer memory at ahigher rate than it is read from the buffer memory, so that the buffermemory always holds a certain amount of data read through the opticalhead when the data is always read from the buffer memory. This allows toput out a reproduced audio signal without interruption even when theoptical head is temporarily disabled by a track jump or the like causedby an external disturbance for example.

In the above-mentioned reproducing apparatus, the operation of theoptical head and the operation of a signal system between the opticalhead and the buffer memory are performed intermittently so that the datais not supplied to the buffer memory in excess of an available writespace in the buffer memory even when the data is written at a hightransfer rate. While the data is not supplied to the buffer memory, theoptical head is kept in a pause state. In the pause state, the opticalhead repeats a one-track jump operation to scan a same track until theamount of data in the buffer memory drops blow a predetermined level.

The duration of time in which the optical head is kept in the pausestate, or a standby state, depends on a size of the buffer memory andsettings of read/write transfer rates. For example, if a 74-minutemagneto-optical disc is reproduced on an apparatus in which data iswritten to the buffer memory at a rate about five times as fast as it isread from it, the writing operation takes only one fifth of an actualoverall reproducing time, or about 14 to 17 minutes in this example,keeping the optical head in the standby state in the remaining fourfifths of the time. In other words, the optical head keeps repeating theone-track jump operation for the four fifths of the total reproducingtime, wasting an electric power of the apparatus for a long time.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an audioreproducing apparatus that operates longer than the related-artapparatus through an efficient power consumption realized by removingthe wasted power consumption.

In carrying out the invention and according to one aspect thereof, thereis provided, as a first constitution, an audio reproducing apparatuscomprising data reading means for reading data from a storage medium,storage means for storing the reproduced data read by the data readingmeans, reproduced signal processing means for putting out, as areproduced audio signal, the reproduced data read from the storagemeans, and control means for controlling operations of the data readingmeans and the storage means with a bit rate for reading the reproduceddata is from the storage means in a unit time set to a lower level thana bit rate for writing the reproduced data to the storage means in aunit time, wherein switch means for stopping or starting supply of anoperating clock for a part or all of the data reading means is providedto be opened or closed by the control means according to an amount ofthe reproduced data in the storage means, controlling a power supply toa part of all of the data reading means.

In carrying out the invention and according to another aspect thereof,there is provided, as a second constitution, an audio reproducingapparatus comprising the same data reading means, storage means,reproducing signal processing means, and control means as thosedescribed in the above-mentioned first constitution with a bit rate forreading reproduced data from the storage means in a unit time set to alower level than a bit rate for writing the reproduced data to thestorage means, wherein the control means controls a supply of anoperating command signal to a driving means according to an amount ofthe reproduced data in the storage means to start or stop an operationof the driving means for sending a drive signal to a driven portion inthe data reading means.

In carrying out the invention and according to still another aspect,there is provided, as a third constitution, an audio reproducingapparatus comprising the same data reading means, storage means,reproduced signal processing means, and control means as those describedin the above-mentioned first constitution with a bit rate for readingreproduced data from the storage means in a unit time set to a lowerlevel than a bit rate for writing the reproduced data to the storagemeans, wherein switch means is provided for stopping a supply of powerto driving means for sending a drive signal to a driven portion in thedata reading means and the control means opens or closes the switchmeans according to an amount of the reproduced data in the storagemeans.

In an audio reproducing apparatus such as mentioned above which isprovided with storage means as a buffer for reproduced output data witha bit rate for reading reproduced data from the storage means in a unittime set to a lower level than a bit rate for writing the reproduceddata to the storage means in a unit time, a certain amount of data isalways stored in the storage means during a reproducing operation whiledata reading means is intermittently operated so that the data is notstored in the storage means more than necessary. Therefore, the datareading means need not be operated except when the data is supplied toit.

In other words, conceptually, executing operations shown in FIG. 1 cansignificantly save a power consumption of the audio reproducingapparatus.

In a reproducing operation, data is read in steps F101 and F102 of FIG.1 to be written to the storage means while the data continuously readfrom the storage means is sent to the reproduced signal processing meansto be put out as an audio signal in step F103, resulting in dataaccumulation because the data writing bit rate is higher than the datareading bit rate. When the data has been accumulated to the full, thedata reading means need not operate for a certain time, or until thedata accumulation drops below a predetermined level. This requires toprovide step F104 for determining whether the data has been fullyaccumulated in the storage means, step F105 for turning off the datareading means for a period of time until the accumulation drops belowthe the predetermined level, step F106 for continuing the operation ofreading data from the storage means and the operation of putting out theaudio signal from the reproduced signal processing means, and step 107for determining whether the data accumulation in the storage means hasdropped below the predetermined level.

The above-mentioned constitution eliminates wasted power consumptioncaused by the unnecessary operation of the data reading means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of the conceptual operation of the audioreproducing apparatus according to the invention;

FIG. 2 is a block diagram illustrating a main portion of a firstembodiment of the audio reproducing apparatus according to theinvention;

FIGS. 3(a), 3(b), 3(c), and 3(d) are a diagram illustrating a buffer RAMread/write operation of the embodiment;

FIGS. 4(a), 4(b), and 4(c) are a diagram illustrating buffer RAMread/write timings of the embodiment;

FIG. 5 is a flowchart of control to be performed at a reproducingoperation of the first embodiment;

FIGS. 6(a) and 6(b) are a diagram explaining a data transfer state atthe reproducing operation of the embodiment;

FIG. 7 is a block diagram illustrating a main portion of a secondembodiment of the audio reproducing apparatus according to theinvention;

FIG. 8 is a diagram illustrating a servo system of the secondembodiment;

FIG. 9 is a flowchart of control to be performed at a reproducingoperation of the second embodiment;

FIG. 10 is a diagram illustrating a mute capability of a variation ofthe second embodiment;

FIG. 11 is a diagram illustrating a servo system of a third embodimentof the audio reproducing apparatus according to the invention; and

FIG. 12 is a flowchart of control to be performed at a reproducingoperation of the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 2 through 6, there is shown a first embodiment of theaudio reproducing apparatus according to the present invention. Thisembodiment is a recording/reproducing apparatus using a magneto-opticaldisc as storage medium. FIG. 2 is a block diagram illustrating a mainportion of the recording/reproducing apparatus.

Referring now to FIG. 2, a system for transferring record/reproductiondata with the magneto-optical disc in the recording/reproducingapparatus generally comprises a data read/write section 30 forreading/writing data on the magneto-optical data, a temporary storage 40for storing data read from the magneto-optical disc or data to bewritten to it, and a record/reproduction signal processor 50 forperforming audio companding and conversion between analog and digitalsignals.

Reference numeral 1 indicates the magneto-optical disc on which audiodata is recorded for example. The disc is loaded into the dataread/write section 30 to be rotationally driven by a spindle motor 2.Reference numeral 3 indicates an optical head through which a laser beamis radiated to the magneto-optical disc 1 at recording or reproducingdata. At recording, it radiates a high-level laser for heating arecording track up to a Curie temperature; at reproducing, it radiates alaser of a relatively low level to detect data out of a reflected ray bymagnetic Kerr effect.

For this purpose, the optical head 3 has a laser diode as laser outputmeans, an optical system comprising a polarization beam splitter and anobjective lens, and a detector for sensing the reflected beam. Theobjective lens 3a is displaceably held in directions radial andperpendicular to the disc 1.

Reference numeral 6 indicates a magnetic head which applies a magneticfield modulated by supplied data to the magneto-optical disc 1 and isarranged opposite to the optical head 3 with the disc in between. Theentire optical head 3 and the magnetic head 6 are adapted to move beyonda displaceable range of the objective lens 3 in the direction radial tothe disc by means of a feed mechanism 5.

Information detected from the magneto-optical disc 1 through the opticalhead 3 in a reproducing operation is sent to an RF amplifier 7. The RFamplifier 7 processes the information to extract a reproduced RF signal,a tracking error signal, a focus error signal, an absolute positionalinformation (recorded on the magneto-optical disc 1 as a pregroup orwobbling group), an address information, and a focus monitor signal. Theextracted reproduced RF signal is sent to an encoder/decoder 8. Thetracking error signal and the focus error signal are sent to a servocircuit 9. The address information is sent to an address decoder 10. Theabsolute positional information and the focus monitor signal are sent toa system controller 11 comprising a microcomputer for example.

The servo circuit 9 generates various servo drive signals from thetracking error signal, the focus error signal, a track jump instructionand a seek instruction from the system controller 11, and rotationalspeed detection information from the spindle motor 2 to control thetwo-axis mechanism 4 and the feed mechanism 5 for focus and trackingcontrol and maintains the spindle motor 2 at a constant angular velocity(CAV) or a constant linear velocity (CLV).

The reproduced RF signal is eight-fourteen modulated (EFM) by theencoder/decoder 8 and then demodulated to be put through decodeprocessing such as CIRC (Cross Interleave Read-solomon Code). Aresultant signal is sent to the temporary data storage 40, ortemporarily written to a buffer RAM 13 through a memory controller 12.It should be noted that transfer of the data from the magneto-opticaldisc 1 through the optical head 3 to the buffer RAM 13, or the datatransfer within the data read/write section 30, is performed at a rateof 1.41 Mbits/s and intermittently.

The data written to the buffer RAM 13 is read at a timing so that thereproduced data is transferred at a rate of 0.3 Mbit/s to be sent to therecord/reproduction signal processor 50, or to an encoder/decoder 14.Then, the data is put through reproduced signal processing such asdecoding for audio compression to be converted by a D-A converter 15into an analog signal. The analog signal is fed from pin 16 to apredetermined amplifier to be put out as reproduction. For example, theanalog signal is put out as left channel and right channel audiosignals.

It should be noted that data read/write operations with the buffer RAM13 are performed by addressing through a write pointer and a readpointer controlled by the memory controller 12.

Referring to FIGS. 3(a), 3(b), 3(c), and 3(d) data read/write operationswith the buffer RAM 13 are conceptually shown supposing that addresses 0through n are set for a data area in the RAM (actually, however, inaddition to the audio signal data, the buffer RAM 13 holds TOC (Table OfContents) data, which is information for controlling record/reproductionoperations, so that a storage area other than for the audio signal datais also set in the RAM).

As shown in FIG. 3 (a), the write pointer W and the read pointer R aresequentially incremented for each of the addresses 0 through n and arereset to address 0 after reaching address n. This technique is known asring control.

When the reproducing operation starts and the data is read from themagneto-optical disc through the data read/write section 30 to be storedin the data temporary storage 40, the write pointer W is sequentiallyincremented as shown in FIG. 3 (b), writing the data to each address. Atalmost the same time (or at a time when the data has been accumulated toa certain extent), the read pointer is sequentially incremented, readingthe data from each address to be sent to the encoder/decoder 14.

The write pointer W is incremented at the timing of 1.41 Mbits/s asmentioned above, while the read pointer R is incremented at the timingof 0.3 Mbit/s, having an address indicated by the write pointer W at acertain time catch up an address indicated by the read pointer R asshown in FIG. 3 (c) (when the write pointer R indicates address x, theaddress indicated by the write pointer W is x-1). In other words, thebuffer RAM 13 has been filled up with the data.

At this point of time, the write pointer W stops incrementing, makingthe data read/write section 30 stop reading data from themagneto-optical disc 1. Meanwhile, the read pointer R continuesincrementing, putting out the reproduced audio signal withoutinterruption.

Then, only the operation of reading the data from the buffer RAM 13continues. Now, suppose that a data accumulation DR in the buffer RAM 13has dropped below a predetermined level at certain point of time asshown in FIG. 3 (d). When the predetermined level has been reached, thedata read/write section 30 starts reading data and write pointer Rstarts incrementing. The reading operation continues until the addressindicated by the write pointer W catches up the the address indicated bythe read pointer R. Thus, the operation of the data read/write section30 to write the reproduced data to the buffer RAM 13 is performed in anintermittent manner.

Referring to FIGS. 4(a), 4(b), and 4(c) a relationship of theabove-mentioned operations is shown. Suppose that the reproducingoperation starts at time t0. The data read/write section 30 startsreading data from the magneto-optical disc 1 to store it to the bufferRAM 13, immediately followed by operations for reading the data from thebuffer RAM 13 and putting out it as a reproduced audio signal (FIG. 4(a) and (b)). Then, if the data accumulation in the buffer RAM 13 hasreached to a full level at time t1 (FIG. 4 (c)), operations to read datafrom the magneto-optical disc and store it to the buffer RAM 13 arestopped. These operations will be not performed until time t2 when thedata accumulation has dropped to a level indicated by YTH. When thislevel has been reached, the data read/write section 30 performs the datareading and storing operations from t2 to t3 at which the dataaccumulation reaches the full level.

Thus, putting out the reproduced audio signal through the buffer RAM 13prevents the reproduced audio signal output from being interrupted by atracking error caused by an external disturbance for example. If thetracking error occurs, a correct tracking position can be accessed whilethe data still remains in the RAM, starting the data reading operationwithout affecting the reproduced output. In other words, the novel setupsignificantly enhances anti-vibration performance of the audiorecording/reproducing apparatus.

Referring again to FIG. 2, the address information and subcode data fromthe address decoder 10 are fed to the system controller 11 through theencoder/decoder 8 to be used for various control operations.Additionally, a lock detection signal of a PLL circuit for generating abit clock for recording/reproducing operations and a monitor signal forchecking whether a frame synchronization signal of the reproduced data(for right and left channels) is missing are fed to the systemcontroller 11.

CK1 indicates a system clock generator. The system controller 11performs control operations based on a clock generated by the CK1. Aclock generator CK2 connected to the encoder/decoder 8 generates a clockfor operating the data read/write section 30. It should be noted that aswitch 8a implemented by an analog switch for example is provided toshut off an oscillation output from the clock generator CK2. The switch8a is adapted to be opened or closed by the system controller 11.

Meanwhile, the system controller 11 generates a laser control signal SLPfor controlling a operation of a laser diode installed on the opticalhead 3. This signal is used to turn on/off laser diode output and switchbetween output at reproduction when a laser power is relatively low andoutput at recording when it is relatively high while the laser diodeoutput is on.

When a recording operation is performed on the magneto-optical disc, arecording signal (an analog audio signal) applied to a pin 17 isconverted through a A-D converter 18 into digital data. The resultantdigital data is then fed to the encoder/decoder 14 to be put throughaudio compression encoding processing. The recording data compressed bythe encoder/decoder 14 is written to the buffer RAM 13 by the memorycontroller and then read from it at a predetermined timing to be fed tothe encoder/decoder 8. The encoder/decoder 8 performs encodingprocessing such as CIRC and EFM on the recording data to send aresultant data to a magnetic head driver 15.

The magnetic head driver 15 supplies a magnetic head drive signal to themagnetic head 6 according to the encoded recording data. That is, themagnetic head 6 applies an N or S magnetic field to the magneto-opticaldisc 1. At the same time, the system controller 11 supplies the controlsignal to the optical head 6 so as to make it output a laser beam at therecording level.

Reference numeral 19 indicates an operator section. Reference numeral 20indicates a display made up of a liquid crystal display for example. Theoperator section 19 has a reproduction key, a stop key, an AMS (AutoMusic Scan) key, a search key, and the like.

Reference numeral 60 indicates a power supply line. A predeterminedvoltage is applied from an internally loaded battery not shown forexample to each circuit over the power supply line 60.

A reproducing operation to be implemented by the embodiment having theabove-mentioned constitution will be described with reference to theflowchart of FIG. 5 and the schematic diagram of FIG. 6.

For example, when a user starts a reproducing operation by means of theoperator section 19, reproduction of data recorded on themagneto-optical disc starts, activating the control operations shown inthe flowchart of FIG. 5.

First, the data read/write section 30 must start operating. The systemcontroller 11 controls the switch 8a in a closed state to allow a datareading operation based on the clock supplied from the clock generatorCK2. Then, the system controller 11 makes the data read/write section 30perform a reproduction initializing operation (F201). That is, thesystem controller 11 turns on the laser output (at the reproductionlevel) of the optical head, instructs the servo circuit to perform afocus search operation, and closes a focus servo loop when the two-axismechanism 4 has been driven to reach a focusing range, turning on focusservo. The system controller 11 instructs the spindle motor 2 to startand controls its speed at a predetermined level. Then the systemcontroller 11 turns on tracking servo. When the above-mentionedinitializing processing has been completed, data can be read from themagneto-optical disc. The system controller 11 then makes the dataread/write section 30 perform a reproduced data reading operation(F202). In other words, a reproduced signal is extracted by the opticalhead 3. It should be noted that it takes about one to two seconds tocomplete the above-mentioned initializing operation.

In addition to performing the reproduced, data reading operation in thedata read/write section 30, the system controller 11 controls data writeand read operations on the data temporary storage 40 through the memorycontroller 12 (F203). In other words, as mentioned above, theencoder/decoder 8 performs CIRC decode processing and EFM demodulationon the audio data extracted by the optical head 3. The resultant data isstored in the buffer RAM 13 at the rate of 1.4 Mbits/s and read from itat the rate of 0.3 Mbit/s. It is obvious that the difference between thedata write rate and the data read rate causes certain amount of dataalways to be left in the buffer RAM 13. If the buffer RAM 13 is 4 Mbitsin storage size, the RAM holds the reproduced data for which it takesabout ten seconds to read it all when full.

During the reproducing operation, the read/write operations on thebuffer RAM 13 are controlled as mentioned above to perform reproductionprocessing on the data read from the buffer RAM 13 by theencoder/decoder 14. The resultant data is then decoded into analog datato be put out from the pin 16 as an audio signal. FIG. 6 (a)conceptually illustrates the flow of the reproduced data.

This operation repeats until the reproduced data is stored in the entirereproduced data storage area of the buffer RAM 13 (until time t1 of FIG.4(a), 4(b), and 4(c). That is, based on the information supplied fromthe memory controller 12, the system controller 11 detects the storageamount of the buffer RAM 18 to determine whether the reproduced data hasbeen fully stored or not.

When the reproduced data is found to have been fully stored, the systemcontroller 11 turns off the switch 8a to shut off the supply of theoperating clock to each circuit of the data read/write section 30. Atthe same time, the system controller 11 turns off the laser power(F205). That is, all circuits of the data read/write section 30 stopoperating and enter in a standby state.

However, since the buffer RAM 13 stores the reproduced data for which ittakes about ten seconds to read it all, the buffer RAM read operationcontinues (F206), providing audio output without interruption. The flowof the reproduced data is conceptually shown in FIG. 6 (b).

Based on the information coming from the memory controller 12, thesystem controller 11 always knows the amount of the reproduced datastored in the buffer RAM 13, so that the system controller 11 comparesthe storage amount with a reference value such as, for example, astorage amount (YTH in FIGS. 4(a, 4(b), and 4(c) for which it takes fiveseconds to read it all (F207). When the storage amount have dropped to alevel at which it takes less than five seconds to read the remainingdata, the system controller 11 turns on the switch 8a again to supplythe operating clock. When the operating clock is supplied, the dataread/write section 30 performs the initializing operation to access apredetermined track position, starting to read the reproduced data froma position at which the switch was turned off previously. It should benoted here that the access operation can be terminated quickly becausethe optical head has been positioned in proximity of the position atwhich the previous reading operation was stopped. Then, the reproduceddata is written to the buffer RAM 13 at the high bit rate (F202 andF203). When the buffer RAM 13 is full, the supply of the clock to thedata read/write section 30 is turned off again (F204 and F205).

Repeating the above-mentioned processing replaces the conventional pausestate (between t1 and t2 in FIGS. 4(a, 4(b), and 4(c) in the dataread/write section 30 with the operation standby state of the dataread/write section 30, allowing the recording/reproducing apparatus ofthe present embodiment to save the power consumed otherwise. Especially,when the data transfer rates and storage size are set as with thepresent embodiment, a power supply off period for the data read/writesection 30 amounts to 4/5 of a reproduced audio signal output time tosignificantly save the power consumption, remarkably extending a servicelife of the internally loaded battery such as a dry cell or the like.For example, the apparatus of the present embodiment operates for morethan two times an operational time of related-art apparatus.

Referring now to FIGS. 7 through 9, there is shown a second embodimentof the audio reproducing apparatus according to the present invention. Aconstitution of this embodiment illustrated in FIG. 7 is almost the sameas that illustrated in FIG. 2, so that description of each circuit blockwill be omitted. However, it should be noted that the switch 8a forshutting off the output of the clock generator CK2 as illustrated inFIG. 2 is not provided in the present embodiment. The servo circuit 9and a driven portion in the data read/write section 30 in the presentembodiment are constituted as shown in FIG. 8.

The servo circuit 9 is supplied with a tracking error signal ET, a focuserror signal EF, and a spindle error signal EPLL as described beforewith respect to the first embodiment. It is also supplied with a controlsignal SSG from the system controller 11 for instructing servoexecution, jump, or initializing operation. These signals are entered ina servo controller 9a to generate each of drive signals (tracking,focus, feed, and spindle) which are fed to a motor driver 9b.

To be controlled by the servo circuit 9 in an actual data readingoperation taking place in the data read/write section 30 are a trackingcoil CTR and a focus coil CFC in the two-axis mechanism 4, a feed motor5, and the spindle motor 2. Based on the drive signals, the motor driver9b supplies a drive power to each of these components.

In the second embodiment, the system controller 11 performs a controloperation at reproduction as shown in FIG. 9. It should be noted thatF302, F303, F304, F306, and F307 in FIG. 9 are the same as F202, F203,F204, F206, and F207 in FIG. 5, so that duplicate description will beomitted.

In this embodiment, the system controller 11 instructs the servocontroller 9a not to perform a motor driving operation during the period(between t1 and t2 in FIG. 4(a), 4(b), and 4(c) in which the dataread/write section 30 need not operate. To be specific, in step F301,the system controller 11 turns on the laser power and supplies the servoexecution control signal SSG to make the servo controller 9a perform arequired operation, supply each drive signal to the motor driver 9b.During the period in which the data read/write section 30 need notoperate, or the full data accumulation in the buffer RAM 13 drops to thepredetermined level YTH, the system controller 11 suspends the servoexecution control signal SSG (F305). Consequently, the servo controller9a does not perform its operation with the drive signal not supplied tothe motor driver 9b, putting each controlled section in a stopped state.At the same time, the laser power is turned off.

Consequently, this embodiment also solves the problem of the powerconsumption wasted during the period in which the data read/writesection 30 need not operate, extending the battery service life as withthe first embodiment.

If a circuit having a mute capability is used for the motor driver 9b ina variation of the second embodiment, the variation can be constitutedso that the system controller 11 supplies a mute control signal SMUTE tothe motor driver 9b as indicated by a dashed line during the period inwhich the data read/write section 30 need not operate.

Referring to FIG. 10 as a circuit block diagram, The mute capability ofthe motor driver 9b is implemented by a switching element Q that canprevent an input drive signal from being put out. When the switchingelement Q is turned on by the mute control signal SMUTE entered from amute pin TM, the drive signal is prevented from being put out. Thetechnique also contributes to saving the power consumption.

Referring to FIGS. 11 and 12, there is shown a third embodiment of theaudio reproducing apparatus according to the present invention. Since aconstitution of the third embodiment is the same as shown in FIG. 7, thedescription of each circuit block will be omitted. The servo circuit 9and driven portion in the data read/write section 30 of this embodimentare constituted as shown in FIG. 11. This constitution is generally thesame as with the second embodiment except a switch SW is provided on apower supply line 60a which supplies a power to the motor driver 9b.

The switch SW comprises a transistor QP, which is part of the powersupply line, and a transistor QS to turn on/off the transistor QP. Aswitch control signal SPOFF is supplied from the system controller 11 toa base of the transistor QS. In other words, when the logic high-levelswitch control signal SPOFF is supplied to the transistor QS to conductit, the transistor QP also conducts to shut off the power to the motordriver 9b.

In the third embodiment, the system controller 11 performs a controloperation at reproduction as shown in FIG. 12. It should be noted thatF402, F403, F406, and F407 in FIG. 12 are the same as F202, F203, F204,F206, and F207 in FIG. 5, so that duplicate description will be omitted.

This embodiment is also constituted so that no motor drive operation isperformed during the period (between t1 and t2 in FIGS. 4(a), 4(b), and4(c) in which the data read/write section 30 need not operate. To bespecific, subsequent to step F401, the system controller 11 does notsupply the logic high-level switch control signal SPOFF to thetransistor QS and turns on the laser output. Consequently, the motordriver 9b is properly powered to supply a drive power to the trackingcoil CTR and focus coil CFC of the two-axis mechanism 4, the feed motor5, and the spindle motor 2 based on each drive signal coming from theservo controller 9a. That is, a data reading operation is performed bythe data read/write section 30.

However, during the period in which the data read/write section 30 neednot operate, or the full data accumulation in the buffer RAM 13 drops tothe predetermined level YTH, the system controller keeps supplying thelogic high-level switch control signal SPOFF to the transistor QS toshut off the power line to the motor driver 9b (F405). This prevents themotor driver 9b from operating, putting each controlled portion in astopped state. At the same time, the laser power is turned off.Consequently, this embodiment also solves the problem of the powerconsumption wasted during the period in which the data read/writesection 30 need not operate, extending the battery service life as withthe first embodiment.

It should be noted that the power supply shut-off may include powerlines to other circuits of the data read/write section 30 than mentionedabove. It should also be noted that the constitution of the switch SW isnot restricted to that composed of transistors.

Meanwhile, in each of the above-mentioned embodiments, the setting valueof the data accumulation by which the timing for restarting theoperation of the data read/write section 30 is determined is notrestricted to a half (5 seconds) of the full capacity as mentionedabove. For example, if a high-speed initializing operation and ahigh-speed access are possible in the data read/write section 30, thetiming for turning on the switch SW may be delayed (for example, theinactive state may be continued until the data accumulation drops to alevel at which it takes four or three seconds to read all remainingdata).

It will be apparent to those skilled in the art that each of theabove-mentioned embodiments may be a reproduction-only apparatus ratherthan the recording/reproducing apparatus. It is also apparent that thepresent invention is applicable to a reproducing apparatus for anoptical disc such as a compact disc (CD) or a digital audio tape (DAT)in addition to the magneto-optical disk. That is, the present inventionis applicable to any reproducing apparatus constituted so that a buffermemory unit is provided at a rear stage of data reading means to alwaysstore a certain amount of data by fast reading the data from the CD orDAT.

While the preferred embodiments of the invention have been describedusing specific terms, such description is for illustrative purpose only,and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the appended claims.

What is claimed is:
 1. Any one of a reproducing apparatus and arecording/reproducing apparatus comprising:data reading means forreading data from a recording medium; driven means, supplied with adrive signal from a driving means, for driving the recording medium withrespect to the data reading means; buffer memory means into whichreproduced data read from the recording medium by the data reading meansis written at a first transfer rate and from which the stored reproduceddata is read at a second transfer rate, the second transfer rate beinglower than the first transfer rate; switching means for selectivelyswitching off power to the driving means such that the driving meansdoes not provide the drive signal to the driven means; and control meansfor controlling an on/off switching operation of the switching meansaccording to an amount of the reproduced data accumulated in the storagemeans.
 2. Any one of a reproducing apparatus and a recording/reproducingapparatus as defined in claim 1, wherein.when the amount of thereproduced data accumulated in the storage means is smaller than apredetermined amount, the control means controls the switching means tosupply power to the drive means, such that the drive means supplies thedrive signal to the driving means, and when the amount of the reproduceddata accumulated in the storage means is greater than the predeterminedamount, the control means controls the switching means to shut off powerto the drive means, such that the drive means does not supply the drivesignal to the driving means.
 3. Any one of a reproducing apparatus and arecording/reproducing apparatus as defined in claim 1, wherein thepredetermined amount is greater than an amount of the reproduced dataread from the storage means, at the second transfer rate, between a timewhen the control means controls the switching means to shut off power tothe driving means, such that the driving means does not provide thedrive signal to the driven means, and a time when the control meanscontrols the switching means to supply power to the driving means, suchthat the driving means provides the drive signal to the driven means. 4.Any one of a reproducing apparatus and a recording/reproducing apparatusas defined in claim 1, wherein the driven means comprises at least anyone or more of a focus coil, a tracking coil, a spindle motor, and afeed motor.